I'm trying to install Ubuntu 13.04 alongside an existing Windows 8 installation. I have shrunk the existing partition where windows is installed in order to make room for Ubuntu.

I booted Ubuntu with the live DVD and it boots without any problem. I then launch the installer, which then probes for existing OS installations on the system. The overview I get mentions my partitions, but it doesn't detect any installed operating system. So I fear that if I continue to install Ubuntu by manually selecting the room where a new partition can be created, my computer will be messed-up.

My computer is UEFI-enabled so I thought the problem could be there. I disabled SecureBoot and activated the option to always launch in CSM modus (which makes the system behave like on older BIOS modus?)

When looking in gparted, I can also so all my partitions.

Does anybody have any idea how come the installer doesn't detect my windows 8? I should mention that there are quite a lot of partitions on the first disk (I think 4 or 5), maybe that's a cause of the problem?